1. Field of the Invention
The subject invention relates to a dynamic sealing device, and more particularly, to a unitized hub seal for installation on a stationary vehicle axle which includes structure for limiting installation load and for preventing rotation of the hub seal components relative to the wheel end and/or the hub.
2. Background of the Related Art
In tractor and trailer wheel end axle assemblies, particularly those employed on large trailers, semi-trailers and tractors, the wheel is mounted on a fixed axle for rotation thereabout. The hub of the wheel defines a lubricant chamber about the end of the axle in association with the wheel bearings. A quantity of lubricant is maintained in the lubricant chamber to continuously bathe the bearings. A hub cap is used to enclose the lubricant chamber and a shaft seal is fit onto the axle to effect a dynamic seal between the axle and the lubricant chamber.
Shaft seals are well known in the art, and generally include a wear member or sleeve and a seal member or casing. The casing is mounted to rotate with the wheel hub relative to the sleeve member. The casing has an outer diameter which is designed to provide an interference fit with the wheel hub and the sleeve is dimensioned to be press fit onto the stationary wheel axle. An early example of a unitized shaft seal in which the wear member and seal member are constructed as a one-piece assembly is disclosed in U.S. Pat. No. 3,685,841 to Keller. Later examples of semi-unitized shaft seals in which the wear member and seal member can be disassembled for repair and inspection are disclosed in U.S. Pat. Nos. 4,208,057 and 4,252,329 to Messenger.
U.S. Pat. No. 4,856,794 to Boyers et al. discloses a unitized seal with axially extending and radially protruding elastomeric ribs formed on the inner wear surface of the sleeve mounted on a vehicle axle for preventing the rotation of the wear sleeve relative to the axle during vehicle operation, i.e., when the casing is rotating with the wheel hub. The axially extending ribs extend to a greater radial height than the radially protruding ribs and thus offer significant axial resistance when the wear sleeve is press fit onto the vehicle axle during installation, unnecessarily increasing axial installation forces. Clearly, there is a need in the art for a unitized seal in which the wear sleeve has anti-rotation structures which reduce, rather than increase, axial installation forces.